Flame-retardant agents for thermoplastic products



United States Patent 3,431,324 FLAME-RETARDANT AGENTS FOR THERMOPLASTIC PRODUCTS Helen Currier Gillham, Princeton, N.J., and Allan Ellis Sherr, Norwalk, (Ionn, assignors to American Cyanamid Company, Stamford, Conn., a corporation of Mame No Drawing. Original application July 30, 1963, Ser. No. 298,577, now Patent No. 3,309,425, dated Mar. 14, 1967. Divided and this application Oct. 28, 1966, Ser. No. 590,230 U.S. Cl. 260-893 6 Claims Int. Cl. C09k 3/28; C07c 29/02, 29/04 ABSTRACT OF THE DISCLOSURE Thermoplastic polymers having improved flame-retardant properties are prepared by blending therewlthminor amounts of a tributylvinylphosphonium bromide or iodide.

This application is a divisional application of copending application Ser. No. 298,577, filed July 30, 1963, now U.S. Patent No. 3,309,425.

This invention relates to flame-retardant compositions. More particularly, this invention relates to flame-retardant compositions comprising thermoplastic polymers containing a flame-retarding amount of a phosphonium salt. Still more particularly, this invention relates to novel flame-retardant compositions comprising thermoplastic polymers containing a flame-retarding amount of a phosphonium salt comprising:

(A) those having the formula R/ cHrCfiz \R wherein R is a saturated, branched or straight chain alkyl radical of from 1 to 8 carbon atoms, inclusive, and X is a bromine or iodine radical,

(B) 1,3,5,7,l0,l0 hexamethyl 2,6,9 trioxa 10- phosphoniatricyclo [3 .3. 1.1 decane iodide,

(C) Ethyltriphenylphosphonium ethyl sulfate or (D) Homopolymers of compounds having the formula wherein Y is a bromine or iodine radical.

The use of various materials incorporated into thermoplastic resins in order to improve the flame retardance thereof has been known in the prior art, Many compounds are commercially available for such a use, among them being chlorostyrene copolymers, chlorinated paraffin wax in admixture with triphenyl stibine, chlorinated paraflins and aliphatic antimonyl compounds, as well as antimony oxide-chlorinated hydrocarbon mixtures. A drawback of these compounds, however, has been the fact that generally a large amount, i.e., upwards of 35%, of additive must be incorporated into the resin in order to make it sufliciently flame retardant. Also these prior art additives tend to crystallize or oil out of the resin after a relatively short time of incorporation. We have now found a group of compounds which may be added to thermoplastic resins in relatively small amounts and still result in the production of satisfactory flame retardant compositions and which will not crystallize or oil out of the resin after incorporation therein.

The production of thermoplastic resin compositions which are flame retardant, i.e., have high resistance to heat, is of considerable commercial importance. For example, such articles as castings, moldings, foamed or laminated structures and the like are required, or at least desired, to be resistant to fire and flame and to possess the ability to endure heat without deterioration. Typical illustrations of such applications can be found in castings for live electrical contacts which should not be ignited or deteriorated by heat and sparks. Structural members such as pipes, wall coverings, wall paneling, windows and items such as ash trays, waste baskets, fibers and the like are further examples of products wherein flame retardance is desirable.

It is therefore an object of the present invention to provide novel flame retardant thermoplastic resin compositions.

It is a further object of the present invention to provide flame retardant compositions comprising thermoplastic polymers and a flame-retarding amount of a phosphonium salt comprising those compounds designated above as A to D.

These and further objects will become more apparent to those skilled in the art upon reading the more detailed description set forth hereinbelow.

THE THERMOPLASTIC POLYMERS The thermoplastic polymers into which the flame retardant agents may be incorporated to produce the novel compositions of the present invention, are generally the vinyl type polymers wherein the monomeric material is polymerized, by any known method, via the vinyl unsaturation therein. Additionally, thermoset type materials may be employed such as the polyester resins, polyurethanes, and the like. Examples of the vinyl type polymers which may be used to form our novel compositions are the vinyl halides, the vinylidene halides, the vinyl acetates, polyvinyl butyral, butadiene copolymers, acrylonitrile-butadienestyrene polymers, the acrylonitriles, etc. Additionally and preferably, one may incorporate the flame retardant agents mentioned above into such polymers as the a-olefin polymers, such as the homopolymers and copolymers etc. containing, as the major constituent, ethylene, propylene, and the like and the acrylates and methacrylate polymers produced from monomers having the formula wherein R -is a hydrogen or methyl radical and R is a hydrogen or an alkyl radical having from 1 to 6 carbon atoms, inclusive. Examples of monomers represented by Formula II include methyl acrylate, ethyl acrylate, npropyl acrylate, isopropyl acrylate, n-butyl acrylate, tbutyl acrylate, isobutyl acrylate, n-arnyl acrylate, t-amyl acrylate, hexyl acrylate and their corresponding alkyl methacrylates.

Additional examples of monomers which may be used to form the thermoplastic vinyl polymers encompassed by the present invention, polymerized either singularly or in combination with each other or with the other compounds set forth hereinabove, are such monomers as the unsaturated alcohol esters, more particularly the allyl, methallyl, vinyl, methvinyl, butenyl, etc, unsaturated esters of aliphatic and aromatic monobasic acids such, for instance,

as acetic, propionic, butyric, crotonic, succinic, glutaric, adipic, maleic, fumaric, itaconic, benzoic, phthalic, terephthalic, benzoylphthalic, etc., acids; the saturated monohydric alcohol esters, e.g., the methyl, ethyl, propyl, isopropyl, butyl, sec.-butyl, amyl, etc., esters of ethylenically unsaturated aliphatic monobasic acids, illustrative examples of which appear above; vinyl cyclic compounds (including monovinyl aromatic hydrocarbons), e.g., styrene, m-, and p-chlorostyrenes, -bromostyrenes, -fluorostyrenes, -methylstyrenes, -ethylstyrenes, -cyanostyrenes, the various poly-substituted styrenes such, for example, as the various di-, tri-, and tetra-chlorostyrenes, -bromostyrenes, -fluorostyrenes, -rnethylstyrenes, -ethylstyrenes, -cyanostyrenes, etc., vinyl pyridine, divinyl benzene, diallyl benzene, the various allyl cyanostyrenes, the various alpha-substituted styrenes and alpha-substituted ring-substituted styrenes, e.g., alpha-methylstyrene, alpha-methylpara-methylstyrene, etc.; unsaturated ethers, e.g., ethyl vinyl ether, diallyl ether, etc.; unsaturated amides, for instance, N-allyl caprolactam, acrylamide, and N-substituted acrylamides, e.g., N-methylol acrylamide, N-allyl acrylamide, N-methyl acrylamide, N-phenyl acrylamide, etc.; unsaturated ketoncs, e.g., methyl vinyl ketone, methyl allyl ketone, etc.; methylene malonic esters, e.g., methylene methyl malonate, etc. and ethylene.

Other examples of monomers that can be used as polymers to form the resin portion of our novel flame-retardant compositions are the vinyl halides, more particularly, vinyl fluoride, vinyl chloride, vinyl bromide, and vinyl iodide, and the various vinylidene compounds, including the vinylidene halides, e.g., vinylidene chloride, vinylidene bromide, vinylidene fluoride, and vinylidene iodide, other comonomers being added, if needed, in order to improve the compatibility and copolymerization characteristics of the mixed monomers.

More specific examples of allyl compounds that can be polymerized to useful polymers, useful in the production of our novel flame-retardant compositions, are allyl alcohol, methallyl alcohol, diallyl carbonate, allyl lactate, allyl alphahydroxyisobutyrate, allyl trichlorosilane, diallyl phthalate, diallyl methylguconate, diallyl tartronate, diallyl tartrate, diallyl mesaconate, the diallyl ester of muconic acid, diallyl chlorophthalate, diallyl dichlorosilane, the diallyl ester of endomethylene tetrahydrophthalic anhydride, triallyl tricarballylate, triallyl cyanurate, triallyl citrate, triallyl phosphate, tetrallyl silane, tetrallyl silicate, hexallyl disiloxane, allyl diglycol carbonate, etc. Other examples of allyl compounds that may be employed are given, for example, in U.S. Patent No. 2,510,503, issued June 6, 1950.

These above mentioned monomers may be polymerized, copolymerized, etc., in any known manner such as by freeradical generating catalysts, irradiation, anion and cation type catalysts and the like, said method of polymerization forming no part of the present invention.

THE PHOSPHONIUM SALTS As mentioned above, we have discovered that the addition of certain phosphonium salts, stable to processing conditions, to a thermoplastic resin results in the production of resinous compositions having excellent flame-retardant properties. These phosphonium salts may be incorporated into the resins in flame-retarding amounts, i.e. generally amounts ranging from about by Weight, to about 35%, by weight, preferably to 25%, by weight, based on the weight of the polymer, have been found sufiicient.

The phosphonium salts can be incorporated into the resins by any known method. That is to say, the flame retardant phosphonium salt additive may be added to the resin by milling the resin and the salt on, for example, a two-roll mill, in a Banbury mixer etc., or the salt may be added by molding the salt and resin simultaneously, extruding the salt and resin or by merely blending the resin in powder form with the salt and thereafter forming the scope of the present invention. Exemplary procedures for the production of compounds represented as A, B, C and D above are as follows:

(A) Generally, these compounds can be produced by the reaction of a secondary phosphine having the formula P-E R with a vinyl halide of the formula CH =CHX wherein R and X are as defined above in regard to Formule I. The reaction is conducted in the presence of a free radical-generating initiator which is nonoxidizing with respect to the secondary phosphine, and at a temperature ranging from about C. to about 200 C. for more than one hour, i.e. 4 to 5 hours. More specific details of such a method of production are set forth, for example, in copending U.S. patent application, Ser. No. 53,902, filed Sept. 6, 1960, now U.S. Patent No. 3,206,496.

Examples of compounds which are represented by Formula I and are therefore useful as flame retardants in producing the novel compositions of the present invention include 1,1,4,4-tetraoctyl-l,4-diphosphoniacyclohexanediiodide,

1,1,4,4-tetraoctyl-l,4-diphosphoniacyclohexanedibromide,

1,1,4,4-tetraheptyl-1,4-diphosphoniacyclohexanediiodide,

1,1,4,4-tetraheptyl-1,4-diphosphoniacyclohexanedibromide,

1, 1,4,4-tetrahexyl-1,4-diphosphoniacyclohexanediiodide,

1,1,4,4-tetrahexyl-1,4-diphosphoniacyclohexanedibromide,

1,1,4,4-tetrapentyl1,4-diphosphoniacyclohexanediiodide,

1,1,4,4-tetrapentyl-1,4-diphosphoniacyclohexanedibromide,

1,1,4,4-tetra-n-butyl-1,4-diphosphoniacyclohexanediiodide,

1, 1,4,4-tetra-n-butyl-1,4-diphosphoniacyclohexanedibromide,

1,1,4,4-tetra-t-butyl-1,4-diphosphoniacyclohexanediiodide,

1 ,1,4,4-tetra-t-butyl-l,4-diphosphoniacyclohexanedibromide,

1,1,4,4-tetraisobutyl-1,4-diphosphoniacyclohexanediiodide,

1,1,4,4-tetraisobutyl-1,4-diphosphoniacyclohexanedibromide,

1, 1,4,4-tetra-n-propyl-1,4-diphosphoniacyclohexanediiodide,

l,1,4,4-tetra-n-propyl- 1,4-dipho sphoniacyclohexanedibromide,

' 1,1,4,4-tetraisopropyl-1,4-diphosphoniacyclohexanediiodide, 1,1,4,4-tetraisopropyl-1,4-diphosphoniacyclohexanedibromide, 1,1,4,4-tetraethyl-1,4-diphosphoniacyclohexanediiodide, 1,1,4,4-tetraethyl-1,4-diphosphoniacyclohexanedibromide, 1,1,4,4-tetramethyl-1,4-diphosphoniacyclohexanediiodide, 1,1,4,4-tetramethyl-1,4-diphosphoniacyclohexanedibromide, 1, l,4,4-tetra(2-ethylhexyl) -l ,4-diphosphoniacyclohexanediiodide, 1,1,4,4-tetra(2-ethylhexyl) -1,4-diphosphoniacyclohexanedibromide and the like.

(B) 1,3,5,7,10,10 hexamethyl 2,6,9 -trioxa-10-phosphoniatricyclo[3.3.l.1 ]decane iodide may be produced by the reaction of 1,3,5,7 tetramethyl-2,6,9-trioxo-10- phosphatricyclo[3.3.l.1 ]decane with methyl iodide by refluxing for about 18 hours. More specific details of the production of this compound can be found, for example, in U.S. Patent No. 3,026,327, issued Mar. 20, 1962.

(C) Ethyltriphenylphosphonium ethyl sulfate may be and the specimen is allowed to burn. If the specimen does not continue to burn after the first ignition it is immediately recontacted with the burner for another 30 second period. If, after the two burnings, the strip is not burned to the 4" mark, the specimen is designated as self-exproduced by heating triphenylphosphine with diethyl sul- 5 tinguishing or flame-retardant. fate in a refluxing solvent such as acetonitrile for about 8 Exam 1e 1 hours. The compound is then recovered, by evaporation p of the solvent, in yields up to about 50% to 100% of Elghty (80) parts of polyethylene and 20 parts of theoretical. 1,l,4,4 tetraoctyl 1,4 diphosphoniacyclohexane di- (D) The homopolymers of tributylvinylphosphonium iodide are milled together on a two roll mill at about 170 iodide and bromide have the structural formula C. The resulting milled composition is molded into strips (111) 5" in length, 0.5 wide and 0.45" in thickness and said (|3H-0Hr strips are then subjected to an art recognized flame-retardance test. The strips pass the test and are therefore ((BH2GH2CH2CH3)3 Y n designated as flame-retardant. wherein n is the number of recurring units in the polymer Followmg the prfcedure offixample the followmg and Y is as defined above. These h omop 01 ym e r 8 may be examples werecarrred out utilizing other flame retardant produced by subjecting aqueous solutions of the tributylf g? various flllermoplait? 5 3 gi T vinylphosphonium monomer to dosage units of radiation su S 9 ese examp es are Sa m a e n or by contacting the monomer with nonoxidizing free each instance the resultant plastic phosphonium salt mlX- radical' generating catalysts under various conditions. passeddflge i g g E g l jfl i More specific details in regard to these procedures are g f zi an f g k j ye set forth in U.S. Patent No. 3,294,764, issued Dec. 27, YPmPY Y m Y E 1966 late); PA=poly(acry11c acid); AN=acrylomtr1le;

Monomers which may be used to produce the homo- ST=styrene polymers represented by Formula III include tributylvinyland BD: butadiene.

TABLE I Example Thermoplastic Flame retardant Percent g llcgd -.f.ig fi xfifi n u 1,1,44-tetraoctyl-1,4-diphosphoniacyclohexane dii0dide 11160 0..-..-..

and AN-ST (25- 0 I 1,1,44-tetraoetyl-1,e-diphosphoniaeyelohexane dibromlde.. 0

1,1,4,4-tetramethy1-1,4-dlphosphoniaeyclohexane diiodide 25 1,1,4&4-tetra-n-butyl-1,4-diphosphoniacyelohexane diiodide. 58 a.. 0 1,litAattgzraisopropyl-l,4-diphosphonlacyclohexane 25 110 9. 10 PE 1,3,5,7,i0,10-hexamethyl-2,6,9-trl0xa-10-phosphoniatrl- 10 11 PP cyl)0[3.3 1 1 7 decane iodide. 20 12:11": Wisteria-Astra ""333:Z6013: 25

33% and AN-ST (25- ii t fl ififxfi 6 Ethcylltriphenylphosphonlum ethyl sulfate 1X Dre 0 0--.-..

and AN-Sl (25 i2 133 13- P01%(trtbutylvinylphosphonium bromide) 17:11::Mixifii'dfifii lfif66 '"'IIIId IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII .III 25 753,; nd AN-ST (25- 19:33:: i i:23123333113231:::::::.iifflfi ifflififiiiiiififfiiflffiiiii::11::::::::::: i?

*U.S. Patent No. 2,439,202. phosphonium bromide and tributylvinylphosphonium iodide.

It should be understood, however, that none of the above enumerated procedures form part of the present invention.

It should be noted that it is also within the scope of the present invention to incorporate such ingredients as plasticizers, dyes, pigments, stabilizers, antioxidants, antistatic agents and the like to our novel compositions.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

Any appropriate flame retardance test may be used to determine the flame retardance properties of any specific compound. One test which is reasonably eflicient is that designated as a modified version of ASTM test D635-56T. The specifications for this test are: a specimen, 5" in length, 0.5" in width and 0.045" in thickness, is marked at the 1" and 4" lengths and is then supported with its longitudinal axis horizontal and its transverse axis inclined at to the horizontal. A Bunsen burner with a 1" blue flame is placed under the free end of the strip and is adjusted so that the flame tip is just in contact with the strip. At the end of 30 seconds, the flame is removed We claim:

1. A flame-retardant composition comprising a thermoplastic polymer produced from at least one ethylenically unsatuarted monomer and a flame retarding amount of a homopolymer of a compound having the formula wherein R is selected from the group consisting of hy- 7 drogen and a methyl radical and R is selected from the group consisting of hydrogen and an alkyl radical having from 1-6 carbon atoms, inclusive.

6. A flame retardant composition according to claim 1 wherein the thermoplastic polymer is a mixture of (A) 6 a butadiene-acrylonitrile copolymer and (B) an acrylonitrile-styrene copolymer, the amount of A and B ranging from about 10-75% to 90-25%, respectively.

References Cited UNITED STATES PATENTS 3,054,698 9/1962 Wagner 260-45] 3,294,764 12/1966 Pellon et al. 260-80 MURRAY TILLMAN, Primary Examiner.

M. J. TULLY, Assistant Examiner.

US. Cl. X.R. 

